The rising popularity of location-based services (LBS) is attributed to the high availability of inexpensive Global Position Systems (GPS), network bandwidth, and mobile devices with expanded storage and increased processing power. Mobile clients frequently use LBS applications to perform spatial queries based on their current locations. A popular type of spatial query is a window query. The query is sent to a server to process and the server returns the result to the client. However, a change in the client's position can invalidate the result.
In the prior art, as the client moves, the query must be continuously reposted to the server to compute and retrieve updated results, incurring high network usage and processing costs. In order to make query processing more efficient, the frequency at which these spatial queries are posted to servers must be reduced. Mobile Window Query (MWQ), also known as Moving Window Query, is defined as the retrieval of a query result along with a safe region. As long as the user stays within the safe region, the mobile client does not need to post another query. The query does not have to be reposted to the server, until the client's position is outside of the safe region.